Hi Julie,
The insects you hear chirruping in the trees are cicadas and you are unlikely to see one never mind be bothered by one.
You are unlikely to be troubled in the daytime except perhaps on the beach when you are still wet after a post-swim shower. Some large fly type things may try to drink from the drops of water on your skin and perhaps fancy a little meat at the same time. They are easily shoo'd away.
You should be taking precautions against bites by the time the sun has nearly set. Get an electric device for your room and keep it on all night. You can buy them at home or at the resort and they take either tablets or liquid, depending on type.
When out in the evening, especially when there is little wind, avoid exposing large areas of skin and use an insect repellant containing a high percentage of deet.
Plakias is a wonderful place and is no better or worse for insects than many other places in the Mediterranean.
It is likely to be hot both day and night in August. Try to avoid top floor rooms which are under a flat concrete roof.
There are few dogs around and those tend to be owned, well fed and wearing collars.
You'll see quite a few cats and sometimes they'll have kittens. They work the tavernas, especially in the evenings. Some people take dried cat food for them. Don't forget they need water too.
Enjoy your holiday.
